1. Field of the Invention
The present invention relates to methods and apparatus for treatment of medical waste and, more specifically, to methods and apparatus for treatment of medical waste that are not dependent upon incineration.
2. Description of the Related Art
The present invention is useful for the effective treatment of a relatively wide variety of medical wastes, but its applicability and effectiveness are particularly noteworthy as to certain classes of medical wastes. There is a lack of uniformity and convention as to the use of certain terms involved in discussions of medical wastes, and for that reason some discussion of nomenclature would facilitate an understanding of the invention.
The term medical waste is defined by the U.S. Environmental Protection Agency (the "U.S. EPA") as any solid waste which is generated in the diagnosis, treatment, or immunization of human beings or animals, in research pertaining to these, or in the production or testing of a biological. 40 C.F.R. Ch.1, .sctn. 259.10(a); U.S. Environmental Protection Agency, Mar. 24, 1989, pp. 12,373-12,374. Biological as used herein refers to preparations made from living organisms and their products, including vaccines, cultures, etc., intended for use in diagnosing, immunizing or treating humans or animals in research pertaining thereto. Such medical waste may derive from a variety of sources, including hospitals, clinics, health maintenance organizations, and the like. Specific examples of medical wastes are provided below.
The term infectious medical waste is defined as waste containing any organism (such as a virus or bacteria) that is capable of being communicated by invasion of or multiplication in body tissues and is capable of causing disease or adverse health impacts in humans. The closely-related term regulated medical waste, used by some synonymously with the term infectious medical waste, is defined by the U.S. EPA as any solid waste [defined in 40 C.F.R. .sctn. 259.10(a)], generated in the diagnosis, treatment, (e.g., provision of medical services), or immunization of human beings or animals, in research pertaining thereto, or in the production or testing of a biological, that is not excluded or exempted under 40 C.F.R. .sctn. 259.30(b), and that is listed in the table of regulated medical waste provided at 40 C.F.R. .sctn. 259.30(a). 40 C.F.R. .sctn. 259.30 (1992).
Technically, medical waste qualifies as infectious or regulated medical waste only if it contains pathogens (microorganisms capable of causing disease) of sufficient quantity and virulence so that human exposure to the medical waste could result in infectious disease. Thus, this class of medical waste is defined in terms of its effect on humans, i.e., the effect of the waste on humans must be known or predicted to classify waste as infectious or regulated medical waste. In view of this definition, the manner in which one determines whether a particular batch of medical waste qualifies as infectious or regulated medical waste has not been reduced to a single, universally-recognized test. Infection Control and Hospital Epidemiology, January 1992, page 40.
One common approach to classification of such wastes involves using a subjective standard in which the waste is deemed to be infectious or regulated medical waste if it is suspected to contain pathogens in sufficient quantity and virulence to cause disease. Infection Control and Hospital Epidemiology, January 1992, page 39.
For purposes of the present invention, the term infectious medical waste as used hereinbelow is interpreted in a broad sense to include the U.S. EPA definition of regulated medical waste at 40 C.F.R. .sctn. 259.10(a) as referred to above, including wastes that meet the subjective standard referred to above. Moreover, the term as used in connection with the invention includes any medical waste that is handled or treated as infectious or regulated medical waste as defined by any of the above definitions.
Infectious or regulated medical waste is commonly divided into seven groups or subcategories. These subcategories, which are summarized, e.g., in the table of regulated medical waste at 40 C.F.R. .sctn. 259.30(a), include the following:
1. Cultures and Stocks
This group includes cultures from medical and pathological laboratories, cultures and stocks of infectious agents from research and industrial laboratories, wastes from the production of biologicals, discarded live and attenuated vaccines, and culture dishes and devices used to transfer, inoculate and mix cultures.
2. Pathological Wastes
This group includes tissues, organs, and body parts and body fluids that are removed during surgery or autopsy, or other medical procedures, and specimens of body fluids and their containers.
3. Human Blood and Blood Products
This group includes liquid waste human blood, products of blood, items saturated and/or dripping with human blood, or items that were saturated and/or dripping with human blood that are now caked with dried human blood, including serum, plasma, and other blood components, and their containers, which were used or intended for use in either patient care, testing and lavatory analysis, or the development of pharmaceutical. Intravenous bags are also included in this-category.
4. Sharps
This group includes sharp items that have been used in animals or human patient care or treatment or in medical research, or industrial laboratories, including hypodermic needles, syringes (with or without the attached needles), pasteur pipettes, scalpel blades, blood vials, needles with attached tubing, and culture dishes (regardless of presence of infectious agents). Also included within this group are other types of broken or unbroken glassware that were in contact with infectious agents, such as used slides and cover slips.
5. Animal Waste
This group includes contaminated animal carcasses, body parts, and bedding of animals that were known to have been exposed to infectious agents during research (including research in veterinary hospitals), production of biologicals, or testing of pharmaceutical.
6. Isolation Wastes
This group includes biological waste and discarded materials contaminated with blood, excretion, exudates or secretions from humans who are isolated to protect others from certain highly-communicable diseases, or isolated animals known to be infected with highly-communicable diseases.
7. Unused Sharps
This category includes unused discarded hypodermic needles, suture needles, syringes, and scalpel blades.
The present invention is well suited for the effective treatment of a wide variety of medical wastes. It is particularly well suited, however, and finds greatest practical advantage, in the treatment of solid or semi-solid infectious medical wastes falling within subcategories 3 and 6 above, i.e., blood and blood products, and isolation wastes. These materials typically comprise synthetic or man-made materials that contain microorganisms, biologicals, or pathogens. Medical waste falling within either of these two subcategories is referred to in this document as treatable medical waste.
Although most infectious medical wastes are generated in hospitals and other health care facilities, relatively little data are available on their specific composition. It is believed that infectious medical wastes typically include a heterogeneous mixture of materials such as plastics, dry cellulosic solids, wet cellulosic solids, and noncombustible materials such as metals. A typical mix of such materials within a batch of medical waste might include, for example, approximately 14% by weight of plastics, about 45% by weight of dry cellulosic material, approximately 18% by weight of wet cellulosic material, and approximately 20% by weight of noncombustibles. Infection Control and Hospital Epidemiology, January 1992, page 40. These wastes often comprise the disposable contents and packaging of single-use products, such as incontinency products, surgeon's instruments, woven towels, non-woven towels, non-woven surgical barrier drapes, non-woven surgical staff apparel, wound dressings, surgical sponges, examination instruments, plastic treatment vessels of many shapes and sizes, patient restraints, etc.
Infectious medical waste contains or is suspected of containing organisms capable of causing disease or adverse health impacts in humans. The term pathogen similarly refers to an agent, organism or microorganism that causes or is capable of causing disease. Examples of pathogens include bacteria, viruses, fungi, mycobacteria and spores. A given item of infectious medical waste typically will have many different types of pathogens on it, and the number of individual pathogenic microorganisms on the item typically will run into the billions. A principal object of the invention is to treat infectious medical waste in a manner that reduces the amount of pathogens so that the waste no longer qualifies as infectious medical waste. Given the extremely large numbers of pathogens encountered, and given the nature of their existence and destruction, measures of the reduction of pathogens in a specific population usually are expressed in statistical terms. In these statistical terms, the amount of pathogens remaining in the population typically are expressed in terms of colony forming units (CFU) per square inch. The State and Territorial Association on Alternate Treatment Technologies recommends requiring an inactivation of vegetable bacteria, fungi, lipophilic/hydrophilic viruses, parasites, and mycobacteria at a 6 log to the 10th power reduction or greater, and inactivation of B. stearothermophilus spores or B. subtilis spores at a 4 log to the 10th power reduction or greater. Technical Assistance Manual: State Regulatory Oversight Of Medical Waste Treatment Technologies, April, 1994, pages 8-12.
Heretofore, the conventional procedure for handling of medical wastes, and particularly for treatable medical wastes, in health care facilities has been as follows. As the medical wastes are created, e.g., in the health care facility, they are placed in red plastic bags. When the red plastic bags become filled, they are taken to a storage area at the health care facility and placed in large plastic drums, typically 44-gallon polyvinyl chloride drums. Lids are secured over the drums to limit odors and to limit vapor and air escape out of the drums. Periodically, the medical waste in the drums is permanently disposed of.
U.S. EPA regulations grant the individual states fairly broad discretion in regulating the handling and treatment of medical wastes. Generally, disposal of infectious medical wastes by dumping in a sanitary landfill without treatment is not permitted. Placing of infectious medical waste in a landfill can be punishable by severe fines and penalties.
The most widely used permanent disposal technique for medical wastes, including treatable medical wastes, is incineration. The incineration is undertaken at special incineration facilities, usually located at a site away from the generating health care facility. At periodic intervals, the medical wastes are picked up by a transporter at the health care facility and taken to the incineration facility. The contents of the drums then are inputted into an incinerator and incinerated. The medical wastes are thereby converted to solids, such as inert ash, and to stack gases that are released into the atmosphere.
The incineration process has been generally disadvantageous in that it is costly. Moreover, incineration brings to bear a host of environmental concerns, most importantly air quality concerns. The U.S. EPA has recently proposed rules pursuant to the 1990 Clean Air Act amendments that would mandate drastic reductions in medical waste incinerator emissions. 60 C.F.R. .sctn. 10654. This is expected to greatly increase the cost of incineration and further reduce its attractiveness as a viable disposal technique.
Steam sterilization of medical wastes has been used as an alternative to incineration. With this approach, the medical wastes are placed in an apparatus similar to an autoclave. In a typical steam sterilization process, the wastes are exposed to steam at approximately 250.degree. F. for about 30 minutes.
Steam sterilization has been disadvantageous for treatment of medical wastes in that it requires relatively large and costly equipment, and in that it is expensive to operate due in large part to the substantial heating requirements. Steam sterilization also is disadvantageous in that it generally does not eliminate highly-objectionable visual evidence of the contamination.
Chemical disinfection, typically accompanied with grinding, is a process in very limited use. This treatment process grinds the wastes in a hammermill in the presence of a chemical disinfectant. This process tends to be expensive.
Thermal inactivation of solid waste, another such process, is accomplished by the application of dry heat in an oven which is usually operated by electricity. This process involves pre-shredding he waste, initially heating it typically with an electric source, and then maintaining a temperature of around 200.degree. F. for approximately two hours in a large enclosed chamber. This process also tends to be expensive.
Irradiation exposes wastes to ultraviolet or ionizing radiation from a source such as cobalt 60 in an enclosed, shielded chamber. Disadvantages are the large initial cost of the equipment, the skilled personnel required for safe operation, and the disposal problem for the decaying radiation source. The method is only effective generally if the ultraviolet radiation reaches the pathogenic waste and there is generally little radiation penetration through the waste which tends not to be ultraviolet transparent.